1. Field of the Invention
This invention relates to the use, as fusion adhesives, of olefin copolymers containing carboxylic acids, carboxylic acid amides and optionally carboxylic acid ester groups, as fusion adhesives.
2. Discussion of the Prior Art
It is known that copolymers containing ethylene, acrylic acid, acrylic amide and acrylic acid esters can be used, in the form of aqueous dispersions, for coating metals. The manufacture of such dispersions and an electrochemical coating process are described in U.S. Pat. No. 3,546,016. Apart from the fact that narrow limits are imposed on the use of dispersions on account of their corrosive properties, the aforementioned coating process requires considerable technological expenditure, which makes its profitability questionable.
German Offenlegungsschrift No. 2 448 342 relates to quaternary ethylene copolymers composed of an ester of an unsaturated carboxylic acid with a saturated alcohol or a vinyl ester of a saturated carboxylic acid, the amide of an unsaturated carboxylic acid and an alkyl vinyl ether, and to the use of the copolymers as adhesives. According to German Offenlegungsschrift No. 2 400 978, terpolymers of ethylene composed of an amide of an ethylenically unsaturated carboxylic acid and an ester of an ethylenically unsaturated carboxylic acid are suitable as adhesives. Although these polymers generally show adequate performance when they are used as adhesives, their resistance to the influence of water is not always adequate, especially at high temperature.
Thus there has existed the need for a fusion adhesive which can be used where there is high mechanical stress and must therefore have certain adhesive properties (scaling resistance values) and which does not deteriorate substantially under severe conditions during prolonged storage in water. The capability of prolonged storage in water can be tested by an ageing test, which consists of storage for 72 hours in water at the high temperature of 60.degree. C. The adhesive should also be manufactured so as to be readily reproducible.
Broadly this invention contemplates a fusion adhesive comprising an olefin copolymer said olefin copolymer comprising 70 to 95% by weight ethylene, 0.5 to 10% by weight of an amide of an unsaturated carboxylic acid and 0.5 to 15% by weight of an unsaturated carboxylic acid. Preferably, the fusion adhesive of the invention additionally contains 0.5 to 15% by weight of an ester of an unsaturated carboxylic acid with a saturated alcohol or a vinyl ester of a saturated carboxylic acid.
This invention further contemplates a method of securing two objects together which comprises disposing between the objects a fusion adhesive comprising an olefin copolymer comprising 70 to 95% by weight ethylene, 0.5 to 10% by weight of an amide of an unsaturated carboxylic acid and 0.5 to 15% by weight of an unsaturated carboxylic acid and fusing said fusion adhesive to said objects. The fusion can be performed by the use of temperature and/or pressure.